1. Field of the Invention
The present invention relates to a distal end structure of an endoscope including an opening of a treatment instrument insertion channel on a distal end of an insertion portion of the endoscope.
2. Description of the Related Art
In recent years, an endoscope has been widely used in a medical field and an industrial field. The endoscope can observe inside of a subject by inserting an elongated insertion portion into a subject.
Note that an example of a well-known endoscope includes an already-known front-view type endoscope provided with an observation lens, an illumination lens, an opening of a treatment instrument insertion channel (hereinafter, called channel opening) on a distal end surface of a distal end portion provided on a distal end side of an insertion portion in a longitudinal axis direction (hereinafter, simply called distal end side), the endoscope observing and treating a site to be examined in front of the distal end surface in the longitudinal axis direction (hereinafter, simply called front) in the subject.
As shown in Japanese Patent Application Laid-Open Publication No. 2010-253069, another example of a well-known endoscope includes an already-known side-view type endoscope provided with an observation lens, an illumination lens, and a channel opening on part of a peripheral surface of a distal end portion of an insertion portion, the endoscope observing and treating a site to be examined on a lateral side with respect to the longitudinal axis direction in the subject.
Here, a technique is well-known, in which a medical side-view type endoscope as disclosed for example in Japanese Patent Application Laid-Open Publication No. 2010-253069 is used, and an already-known elongated stent placed in, for example, a bile duct and configured to expand the diameter of a stenosis of the bile duct is recovered through the opening of the treatment instrument insertion channel.
Specifically, in the technique, an already-known recovery treatment instrument, such as a snare and grasping forceps, is first inserted into the treatment instrument insertion channel from an operation portion side of the endoscope, and a distal end side of the recovery treatment instrument is projected from the channel opening.
Subsequently, the stent is held on the distal end side of the recovery treatment instrument, and lastly, the stent is drawn into the treatment instrument insertion channel along with the recovery treatment instrument through the channel opening to recover the stent.
Note that at the recovery, the stent is delivered across the channel opening in the bile duct. In a state that the distal end side of the recovery treatment instrument holds near the center of the stent, drawing force in drawing the recovery treatment instrument and each opening edge portion of the channel opening are used to draw the stent into the treatment instrument insertion channel through the channel opening while the stent is folded in half near the center.